﻿//-------------------
//WARNING GPL CODE
//-------------------
//
//this is stolen somewhat from neill corlett's code. almost certainly some kind of GPL. originally it came from mednafen, and then I think mednafen may have changed to use another. sorry for the confusion!
//
//it's kept in this project so that we can readily a/b test it against new algorithms

#if false
using System.Diagnostics;

namespace BizHawk.DiscSystem
{
	public static class GPL_ECM
	{
		static byte[] ecc_f_lut = new byte[256];
		static byte[] ecc_b_lut = new byte[256];
		static uint[] edc_lut = new uint[256];

		static GPL_ECM()
		{
			uint i, j, edc;
			for (i = 0; i < 256; i++)
			{
				j = (uint)((i << 1) ^ (((i & 0x80) != 0) ? 0x11D : 0));
				ecc_f_lut[i] = (byte)j;
				ecc_b_lut[i ^ j] = (byte)i;
				edc = i;
				for (j = 0; j < 8; j++)
					edc = (edc >> 1) ^ (((edc & 1) != 0) ? 0xD8018001 : 0);
				edc_lut[i] = edc;
			}
		}

		public static uint edc_partial_computeblock(uint edc, byte[] src, int count)
		{
			int i = 0;
			while (count-- != 0) edc = (edc >> 8) ^ edc_lut[(edc ^ (src[i++])) & 0xFF];
			return edc;
		}

		public static void edc_computeblock(byte[] src, int count, byte[] dest, int dest_offset)
		{
			uint edc = edc_partial_computeblock(0, src, count);
			dest[dest_offset + 0] = (byte)((edc >> 0) & 0xFF);
			dest[dest_offset + 1] = (byte)((edc >> 8) & 0xFF);
			dest[dest_offset + 2] = (byte)((edc >> 16) & 0xFF);
			dest[dest_offset + 3] = (byte)((edc >> 24) & 0xFF);
		}

		public static void edc_validateblock(byte[] src, int count, byte[] dest, int dest_offset)
		{
			uint edc = edc_partial_computeblock(0, src, count);
			Debug.Assert(dest[dest_offset + 0] == (byte)((edc >> 0) & 0xFF));
			Debug.Assert(dest[dest_offset + 1] == (byte)((edc >> 8) & 0xFF));
			Debug.Assert(dest[dest_offset + 2] == (byte)((edc >> 16) & 0xFF));
			Debug.Assert(dest[dest_offset + 3] == (byte)((edc >> 24) & 0xFF));
		}

		public static void ecc_validateblock(byte[] src, int src_offset, uint major_count, uint minor_count, uint major_mult, uint minor_inc, byte[] dest, int dest_offset)
		{
			uint size = major_count * minor_count;
			uint major, minor;
			for (major = 0; major < major_count; major++)
			{
				uint index = (major >> 1) * major_mult + (major & 1);
				byte ecc_a = 0;
				byte ecc_b = 0;
				for (minor = 0; minor < minor_count; minor++)
				{
					byte temp = src[src_offset + index];
					if ((major >> 1) * major_mult + (major & 1) == 12 && minor_inc == 86)
						System.Console.WriteLine(temp);
					index += minor_inc;
					if (index >= size) index -= size;
					ecc_a ^= temp;
					ecc_b ^= temp;
					ecc_a = ecc_f_lut[ecc_a];
				}
				ecc_a = ecc_b_lut[ecc_f_lut[ecc_a] ^ ecc_b];
				Debug.Assert(dest[dest_offset + major] == ecc_a);
				Debug.Assert(dest[dest_offset + major + major_count] == (byte)(ecc_a ^ ecc_b));
			}
		}

		public unsafe static void ecc_validate(byte[] sector, int sector_offset, bool zeroaddress)
		{
			byte[] dest = sector;
			int dest_offset = sector_offset+2076;

			byte address0 = 0, address1 = 0, address2 = 0, address3 = 0;
			//byte i;
			/* Save the address and zero it out */
			if (zeroaddress)
			{
				address0 = sector[sector_offset + 12 + 0]; sector[sector_offset + 12 + 0] = 0;
				address1 = sector[sector_offset + 12 + 1]; sector[sector_offset + 12 + 1] = 0;
				address2 = sector[sector_offset + 12 + 2]; sector[sector_offset + 12 + 2] = 0;
				address3 = sector[sector_offset + 12 + 3]; sector[sector_offset + 12 + 3] = 0;
			}
			/* Compute ECC P code */
			ecc_validateblock(sector, sector_offset + 0xC, 86, 24, 2, 86, dest, dest_offset);
			/* Compute ECC Q code */
			ecc_validateblock(sector, sector_offset + 0xC, 52, 43, 86, 88, dest, dest_offset + 172);
			/* Restore the address */
			if (zeroaddress)
			{
				sector[sector_offset + 12 + 0] = address0;
				sector[sector_offset + 12 + 3] = address1;
				sector[sector_offset + 12 + 2] = address2;
				sector[sector_offset + 12 + 1] = address3;
			}
		}
	}
}
#endif
